A backlight module is one of the key components of a liquid crystal display device. Because liquid crystals do not emit any light by themselves, the main function of a backlight module is providing a uniform high brightness light emitter for a liquid crystal panel. The basic principle is converting a common point light emitter or a linear light emitter to a uniform high brightness surface light emitter through an effective optical structure, so that the display panel can normally display images. The backlight modules are not only applied in liquid crystal televisions and liquid crystal devices, but also can be applied in display devices requiring backlights such as digital photo frames, electronic papers, mobile phones and the like.